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Energy storage capacitive thin films.

Author

Lee, Lai Yuan.

Date of Issue

2008

School

School of Electrical and Electronic Engineering

Abstract

Progress in supercapacitor technology can benefit by moving from conventional to nanostructured electrodes. However, their main drawback lies in the use of liquid electrolytes, which can become hazardous in case of thermal runaway referring to a situation where an increase in temperature changes the conditions in such way that it causes a further increase in temperature leading to a destructive result (vaporization of the solvent, inflammation, explosion of the supercapacitor). Solid electrolytes of supercapacitors are advantageous over liquid electrolytes. The main advantages produced by the use of solid electrolytes will be lower internal corrosion, minor leakage of dangerous substances, increased device safety and flexibility, thinner configuration, major compactness, and easier packaging.
The purpose of this FYP project is to fabricate the high energy storage capacitive thin films, and explore the effect of SnO2 nanorods on the capacitive properties of capacitor. Ba0.65Sr0.35TiO3 (BST) thin films were successfully prepared using Spin-coating and RF magnetron sputtering, and the effects of sintering and sputtering temperature on the microstructure and capacitive properties of the BST thin films were investigated. The effect of SnO2 nanorods as the bottom electrode on the microstructure and capacitive properties of the BST film capacitor was also studied. The results show for BST thin films deposited by RF sputtering, their crystalline temperature (470 ºC) is far lower than that (600 ºC) of the spin-coated films. For the fabrication of thin film, RF magnetron sputtering which is simple and clear is much better than spin-coating. The dielectric properties for the BST thin films prepared by RF sputtering are also much better than those of the thin films prepared by spin-coating. For the BST film sputtered at the temperature of 620 ºC , the large dielectric constant (295) and low loss (0.042) at 100 kHz, and high dielectric tunability up to 38% were achieved at a low applied voltage of 5 V (147 kV/cm). The investigation of dielectric properties of BST film deposited on SnO2/SiO2/Si substrate by RF sputtering shows, SnO2 nanorods added on Si/SiO2 substrate can improve the dielectric properties of the BST capacitors due to the good microstructure (high dense and no porosity) for the BST thin film with SnO2 nanorods, prepared by RF sputtering. The further work on the effect of SnO2 nanorods on the capacitive properties of capacitors is suggested to be done.